MongoDB聚合方法

Question

例如

如何显示来自 db.anycollection.aggregate(..) 的结果

 // drop collectio
db.collections.drop()
// insert data
db.collections.insertMany([
{cust_id: "A123", anount: 500, status : "A"},
{cust_id: "A123", anount: 250, status : "A"},
{cust_id: "B212", anount: 200, status : "A"},
{cust_id: "A123", anount: 300, status : "D"}
])
// aggregate throuhgh thr collection
var results = db.collection.aggregate([
   {$match:{status:"A"}},
   {$group:{_id: "$cust_id", total:{$sum:"$amount")))


  ])

Answer 1

你可以这样做：-

var Member = mongoose.model("Members", memberSchema );

Member.aggregate(
{ "$match": { "_id": userid } },
{ "$unwind": "$friends" },
{ "$match": { "friends.status": 0 } },
function( err, data ) {

if ( err )
  throw err;

console.log( JSON.stringify( data, undefined, 2 ) );

}

通过这样做，您可以显示汇总结果。